1. Field of the Invention
This invention describes a manufacture technique of stretchable circuit board with the capability of large deformation. The stretchable circuit board exhibits stable electrical and mechanical properties even under various conditions such as bending, twisting, or off-axis stretching.
2. Description of the Related Art
A printed circuit board (PCB), in which a copper line is thinly printed, can mechanically support and electrically connect various electronic components, such as a semiconductor, a condenser and a resistor. The printed circuit board is used to decrease the size of an electronic device and to increase the performance.
A printed circuit board is widely employed as the carrier of integrated circuits (ICs) in electronic devices, which are fundamentally rigid and planar. However, human bodies and nature are shown in the form of soft curves usually. Therefore, the printed circuit boards without flexibility seriously limit its applications. In order to overcome the mismatch between the rigid plane and the soft curve, various flexible substrates are developed to realize the commercial wearable device as a next-generation smart device. A conventional method of manufacturing the flexible board is used a metal to deposit on the surface of a flexible substrate. Conventionally, a metal such as gold (Au), platinum (Pt), or silver (Ag) is deposited in a vapor state on the surface of a substrate such as polydimethylsiloxane (PDMS), silicone rubber, or acryl rubber. After deposition, a pattern is formed on the substrate and to realize the flexible circuit board.
Although the fabricated circuit board exhibits stable electrical properties under bending deformation, the metal pattern layer is stripped from the surface of a flexible substrate under tensile deformation of 10% or more, undesirably deteriorating electrical conductivity.
Therefore, stripping problems between the metal layer and the stretchable substrate are conventionally solved by mixing a polymer with carbon nanotubes (CNT), carbon black (CB), or graphite to form a circuit pattern using the mixture conductive material. The fabricated stretchable circuit board advantageously exhibits stable electrical properties even under a tensile deformation of 100% or more. However, the electrical conductivity is undesirably low.
Recently, a variety of stretchable electronic devices based on a wave-shaped serpentine pattern have been reported by Wagner et al. and Rogers et al. The stretchable electronic device requires complicated processing because a wave-shaped pattern has to be formed.
In this regard, Korean Patent Application Publication Nos. 10-2010-0123755 (Stretchable and Foldable Electronic Devices) and 10-2014-0121325 (Stretchable Electric Device and Manufacturing Method of the Same) are provided.